LG GSA-4165B 사용자 설명서
22
3) CD-RW Disc
4. Reading process of Optical Disc
Laser Beam
Groove
Substrate
(Polycarbonate)
(Polycarbonate)
Recording Layer
Dielectric Layer(TL)
Dielectric Layer(UL)
Protective Layer
Label Printing
• It is composed of polycarbonate layer, alloy(silver, arsenic) layer, aluminum reflectivity layer, protective layer.
• An crystalized alloy layer is transformed into noncrystalized by the laser heat. Therefore, writing and reading
• An crystalized alloy layer is transformed into noncrystalized by the laser heat. Therefore, writing and reading
is enabled by the difference of reflectivity.
• It is possible to overwrite about 1000 times.
• Laser Wavelength : 780 nm, Laser Power (Read) : 1.0mW
• Recording Power : Erase (4~18mW), Write (6~45mW)
• When disc rewriting, new data is overwritten previously recorded data.
• Polycarbonate layer has a Pre-Groove which make a track.
• Laser Wavelength : 780 nm, Laser Power (Read) : 1.0mW
• Recording Power : Erase (4~18mW), Write (6~45mW)
• When disc rewriting, new data is overwritten previously recorded data.
• Polycarbonate layer has a Pre-Groove which make a track.
Lens
H
D
Beam
Spot
Spot
Focusing
Lens
Lens
Laser Spot
at Constant
Read Intensity
at Constant
Read Intensity
Reflected
Light
Signal
Light
Signal
Laser Spot
Position
(Time)
Position
(Time)
Previously Recorded Marks
Groove
Land
Mirror
I
3
I
top
I
11
I
G
I
L
I
0
Numerical aperture:
NA
=nsin
θ
,
n
: Refractive index
Focus depth :
H
=
λ
/
NA
laser spot diameter :
D
=
λ
/
NA
2
θ